Powdery mildew is an important disease of crop plants. In strawberry, the disease is
caused by the obligate biotrophic fungus Podosphoera ophonis (syn: Sphoeratheco
mocu/oris f. sp. Fragorioe) and causes significant economic loss in the cultivated
strawberry. This study used the diploid species Fragorio vesco as a model to study plant
pathogen interactions. Initial studies involved in the identification of mildew resistance
locus 0 (MLO) genes in the diploid species, F. vesco f. vesco and identified 17 FvMLO
genes. Real-time quantitative PCR (qRT-PCR) results showed differential expression of 12
FvMLO genes in four strawberry varieties, F. vesco f. vesco (Fv), F. vesco ssp. vesco
accession Hawaii 4 (HW), F. vesco f. semperf/orens line "Yellow Wonder 5AF7" (YW) and
Eluica (octoploid strawberry). The FvML03 gene which is orthologous to the Arabidopsis
AtML02, AtML06 and AtML012 and tomato S/ML01 genes required for powdery mildew
susceptibility was highly expressed (164 fold) in YW compared to other FvMLO genes
across varieties. The results showed that FvMLO genes can be used as potential
candidates to engineer powdery mildew resistance in strawberry based on MLO
suppression. To investigate the molecular mechanism underlying strawberry-powdery
mildew interaction, RNA-seq was employed to generate a large transcriptome dataset in
HW and YW at 1 d and 8 d after powdery mildew infection. We identified about 999
million (92%) reads mapped to the F. vesco genome. Transcripts were identified from a
total of 23,470 and 23,464 genes in HW and YW, respectively at all three stages (control,
1DAI and 8DAI). Differential gene expression analysis identified 1,567, 1,846 and 1,145
upregulated genes between control and 1DAI, control and 8DAI, and 1DAI and ! lDAI,
respectively in HW. Similarly, 1,336, 1,619 and 968 genes were upregulated in YW. Also
646, 1,098 and 624 down regulated genes were identified in HW, while 571, 754 and 627
genes were downregulated in YW between all three stages, respectively. The study also
investigated differentially expressed genes (log2 fold changes